Sometimes aquariums will encounter un-expected algae blooms and other events that may jeopardize the health and beauty of your aquarium. These events may be caused by microorganisms such as bacteria, algae, and parasites floating in your water. UV Sterilizers use a special fluorescent lamp that will eradicate and control these free-floating microorganisms as well as disease causing pathogens when water is pumped through the unit. SunSun 13 Watt UV Replacement Bulb compatible with the following products: SunSun JUP-23, JBJ 13W Submersible UV Sterilizer, Jebao PU13 clarifier, Jebao CF-10, CF-20, CF-30, PF-30, ViaAqua 13W UV Clarifier, AQUATOP 13W UV Filter, CUV-113